EP1623908A1 - Elektrische servolenkvorrichtung - Google Patents

Elektrische servolenkvorrichtung Download PDF

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Publication number
EP1623908A1
EP1623908A1 EP04728046A EP04728046A EP1623908A1 EP 1623908 A1 EP1623908 A1 EP 1623908A1 EP 04728046 A EP04728046 A EP 04728046A EP 04728046 A EP04728046 A EP 04728046A EP 1623908 A1 EP1623908 A1 EP 1623908A1
Authority
EP
European Patent Office
Prior art keywords
portions
worm
gear
electric power
power steering
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP04728046A
Other languages
English (en)
French (fr)
Other versions
EP1623908A4 (de
EP1623908B1 (de
Inventor
Akihiko c/o Koyo Seiko Co. Ltd. Shiina
Hiroaki c/o KOYO SEIKO CO. LTD. SHINTO
Mitsuharu c/o KOYO SEIKO CO. LTD. MINAMI
Noritake c/o KOYO SEIKO CO. LTD. OKAWA
Masayoshi c/o KOYO SEIKO CO. LTD. SAKUDA
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
JTEKT Corp
Original Assignee
Koyo Seiko Co Ltd
JTEKT Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koyo Seiko Co Ltd, JTEKT Corp filed Critical Koyo Seiko Co Ltd
Priority to EP11170816A priority Critical patent/EP2371675B1/de
Publication of EP1623908A1 publication Critical patent/EP1623908A1/de
Publication of EP1623908A4 publication Critical patent/EP1623908A4/de
Application granted granted Critical
Publication of EP1623908B1 publication Critical patent/EP1623908B1/de
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H1/00—Toothed gearings for conveying rotary motion
    • F16H1/02—Toothed gearings for conveying rotary motion without gears having orbital motion
    • F16H1/04—Toothed gearings for conveying rotary motion without gears having orbital motion involving only two intermeshing members
    • F16H1/12—Toothed gearings for conveying rotary motion without gears having orbital motion involving only two intermeshing members with non-parallel axes
    • F16H1/16—Toothed gearings for conveying rotary motion without gears having orbital motion involving only two intermeshing members with non-parallel axes comprising worm and worm-wheel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
    • B62D5/0409—Electric motor acting on the steering column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C25/00—Bearings for exclusively rotary movement adjustable for wear or play
    • F16C25/06—Ball or roller bearings
    • F16C25/08—Ball or roller bearings self-adjusting
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/08—Structural association with bearings
    • H02K7/081—Structural association with bearings specially adapted for worm gear drives
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2361/00—Apparatus or articles in engineering in general
    • F16C2361/61—Toothed gear systems, e.g. support of pinion shafts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2380/00—Electrical apparatus
    • F16C2380/26—Dynamo-electric machines or combinations therewith, e.g. electro-motors and generators
    • F16C2380/27—Motor coupled with a gear, e.g. worm gears
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H57/00—General details of gearing
    • F16H57/02—Gearboxes; Mounting gearing therein
    • F16H57/021—Shaft support structures, e.g. partition walls, bearing eyes, casing walls or covers with bearings
    • F16H2057/0213—Support of worm gear shafts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H55/00—Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
    • F16H55/02—Toothed members; Worms
    • F16H55/22—Toothed members; Worms for transmissions with crossing shafts, especially worms, worm-gears
    • F16H55/24—Special devices for taking up backlash

Definitions

  • the present invention relates to an electric power steering device that uses an electric motor as a source for generating a steering assistance force.
  • This electric power steering device is configured to detect the steering torque applied to the input shaft depending on the relative angular displacement amount between the input shaft connected to the steering wheel and the output shaft coaxially connected to the input shaft via a torsion bar and to drive a steering-assisting electric motor on the basis of the detected torque.
  • the rotation force of the electric motor is transmitted to a steering mechanism via a reduction gear mechanism, and the operation of the steering mechanism depending on the rotation of the steering wheel is assisted, whereby the driver's load for steering is reduced.
  • the reduction gear mechanism comprises a worm serving as a small gear and connected to the driving shaft of the electric motor and a worm gear serving as a large gear and meshing with the worm, and this worm wheel is fitted on and secured to the intermediate portion of the output shaft.
  • the worm has shaft portions protruding from both end portions of the tooth portion (gear body) thereof, and the shaft portions are rotatably inserted into the inner rings of roller bearings so as to be born, respectively.
  • the worm of the electric power steering device configured as described above is born so that the shaft portions at both end portions cannot move in the axial direction with respect to the roller bearings being used respectively to bear the shaft portions.
  • the device is configured that, when the steering wheel is steered left or right from the steering neutral position, steering assistance is carried out by the rotation of the electric motor in the early stage of the start of the steering, the steering assistance is carried out even if the steering angle of a vehicle running at high speed is a small angle of approximately one degree, for example; hence, steering feeling is deteriorated.
  • conventional electric power steering devices are generally configured that the electric motor is not driven when the steering angle is a small angle of approximately one degree, and that the electric motor is driven only when the steering angle exceeds an appropriate steering angle.
  • the steering force of the steering wheel is transmitted to the driving shaft of the electric motor via the input shaft, the torsion bar, the output shaft, the worm wheel and the worm, whereby the driving shaft is rotated.
  • the load for rotating the driving shaft of the electric motor is applied reversely to the steering wheel via the worm, the worm wheel, the output shaft, the torsion bar and the input shaft; hence, the steering load becomes large and steering feeling is deteriorated.
  • limiting members for limiting the deflection amounts of the belleville springs are provided between the inner rings of the roller bearings and the worm.
  • each limiting member is disposed inside the inner fringe or outside the outer fringe of the belleville spring.
  • the limiting member is disposed inside the inner fringe of the belleville spring, it is necessary to increase the diameter of the belleville spring so that the limiting member can pass through the inside of the inner fringe of the belleville spring.
  • the limiting member is disposed outside the outer fringe of the belleville spring, it is necessary to increase the diameter of the worm or the size of the housing incorporating the worm so that the limiting member can be disposed.
  • the limiting members for the belleville springs it is inevitable that the size of the worm portion is increased in comparison with the case where the limiting members for the belleville springs are not provided.
  • Japanese Patent Application Laid-Open No. 11-43062 (1999) described above discloses a configuration wherein O rings are provided on the inner circumferential sides of the inner rings and on the outer circumferential sides of the outer rings of the roller bearings for bearing the worm.
  • the meshing noise at the meshing portion can be reduced by using the flexibility of the O rings owing to the meshing reaction forces applied to the meshing portion of the worm and the worm wheel.
  • this kind of configuration causes a problem of increasing the backlash amount at the meshing portion owing to the abrasion of the teeth of the worm and the worm wheel.
  • the belleville springs are formed into a taper shape from the inner fringe to the outer fringe as described above, if the belleville spring is assembled in such a way that the direction of the taper is reversed, the function of the belleville spring is lowered or the belleville spring does not function at all. In such a case, it becomes necessary to reassemble the belleville spring.
  • an electric power steering device capable of being provided with limiting members for limiting the deflection amounts of circular elastic bodies (for example, belleville springs) without increasing the size of a small gear portion (for example, a worm).
  • an electric power steering device capable of raising the durability of elastic bodies for reducing the steering load in a steering range wherein a steering-assisting electric motor is not driven and also capable of not increasing the backlash amount at the meshing portion of gears even in the case where the abrasion amounts of the teeth of the gears increase.
  • an electric power steering device capable of preventing the plastic deformation of elastic bodies for reducing the steering load in a steering range wherein a steering-assisting electric motor is not driven, capable of raising the durability thereof, and capable of eliminating the necessity of reassembling the elastic bodies.
  • an electric power steering device capable of raising the durability of elastic bodies for reducing the steering load in a steering range wherein a steering-assisting electric motor is not driven, capable of eliminating the necessity of reassembling the elastic bodies, and capable of being provided with the elastic bodies without increasing the size of a small gear portion.
  • a first invention of the electric power steering device in accordance with the present invention comprises: a small gear having a gear body which is rotated by an electric motor and on which a tooth portion is formed and shaft portions respectively formed so as to protrude from both end portions of said gear body and being smaller in diameter than said gear body; bearings for respectively bearing both said shaft portions of said small gear so that said small gear can move in an axial direction; two circular elastic bodies, respectively externally fitted on both said shaft portions of said small gear, for suppressing movement of said small gear in the axial direction to shaft end portions; and a large gear meshing with the tooth portion of said gear body of said small gear and connected to a steering means; and being configured to assist steering by rotation of said electric motor, and is characterized by comprising: limiting members, provided at portions along outer circumferences of said shaft portions respectively at its both end portions of said gear body, for limiting deflection amounts of said elastic bodies.
  • the limiting members for limiting the deflection amounts of the circular elastic bodies can be provided at portions along the outer circumferences of the shaft portions respectively at both end portions of the gear body without increasing the size of the small gear portion.
  • a second invention of the electric power steering device in accordance with the present invention is characterized that, in accordance with the first invention, said circular elastic body has flat portions formed on inner circumferential side, and a tapered portion formed on outer circumferential side and connected to said flat portions.
  • the deflection amounts of the circular elastic bodies are limited by the limiting members; hence, the plastic deformation of the circular elastic bodies can be prevented or the durability thereof can be improved.
  • the flat portions being formed flat are provided on the inner circumferential side of the circular elastic body, and these flat portions make contact with the limiting member, and the deflection amount of the tapered portion is limited; hence, the limiting members can be provided without increasing the size of the small gear portion.
  • a third invention of the electric power steering device in accordance with the present invention is characterized that, in accordance with the second invention, said bearings are roller bearings, said circular elastic body is a belleville spring having said flat portions at its end portions and multiple flexible pieces formed so as to protrude from said tapered portion to the inner circumferential side, said limiting members are disposed between inner rings of said roller bearings and its both end portions of said gear body of said small gear, respectively, and said inner rings of said roller bearings are configured so as to make contact with protruding side faces of said flat portions, and said limiting members are configured so as to make contact with rear faces of said protruding side faces.
  • the flat portions of the circular elastic body can be used as seats for the inner ring, and the flat portions can be made face contact with one side face of the inner ring.
  • the belleville springs do not require support members for supporting the flexible pieces, the stability of the belleville springs can be raised. Therefore, the number of components can be reduced although the belleville springs are provided, and the cost can be reduced in comparison with the case wherein supporting members for suppressing the flexible pieces are used.
  • a fourth invention of the electric power steering device in accordance with the present invention is characterized that, in accordance with the first invention, said bearings are configured so as to be movable in a direction wherein a distance between a rotational center of said small gear and a rotational center of said large gear becomes long or short, and an energizing means for energizing said bearings in a direction wherein the distance between the rotational center of said small gear and the rotational center of said large gear becomes short is provided.
  • the elastic bodies are deflected by forces applied to the small gear in the axial direction.
  • the steering load in the steering range wherein the electric motor is not driven can be reduced, and steering feeling is improved.
  • the elastic bodies are deflected by forces applied to the small gear in the axial direction, since the deflection amounts of the elastic bodies are limited by the limiting members, the durability of the elastic bodies is improved.
  • a fifth invention of the electric power steering device in accordance with the present invention is characterized that, in accordance with the fourth invention, said bearings are roller bearings, and said circular elastic bodies are belleville springs disposed between inner rings of said roller bearings and end portions of said gear body of said small gear.
  • the step portions at both end portions of the gear body can be used as seats for receiving the elastic bodies; hence, the structure for supporting the elastic bodies can be simplified, and the machinability and assembly workability are improved.
  • a sixth invention of the electric power steering device in accordance with the present invention is characterized that, in accordance with the first invention, said bearings are roller bearings, and said circular elastic bodies are installed in inner rings of said roller bearing.
  • the elastic bodies are deflected by forces applied to the small gear in the axial direction.
  • the steering load in the steering range wherein the electric motor is not driven can be reduced, and steering feeling is improved.
  • the elastic bodies are deflected by forces applied to the small gear in the axial direction, since the deflection amounts of the elastic bodies are limited by the limiting members, the durability of the elastic bodies is improved.
  • the elastic bodies are assembled in the inner rings of the roller bearings, it is not necessary to assemble the elastic bodies individually. Therefore, the possibility of causing improper assembly of the elastic bodies during manufacturing is eliminated; hence, it is not necessary to reassemble the elastic bodies, and the assembly workability is improved.
  • a seventh invention of the electric power steering device in accordance with the present invention is characterized that, in accordance with the sixth invention, circular grooves are formed on outer circumferential faces of said inner rings of said roller bearings between raceway grooves and side faces on sides of said gear body of said small gear, and said circular elastic bodies are belleville springs whose inner circumferential portions are formed so as to be fitted in said circular grooves formed on the outer circumferential faces of said inner rings of said roller bearings.
  • the belleville springs can be assembled beforehand in the roller bearings by externally fitting the fitting inner circumferential portions of the belleville springs in the circular grooves, the belleville springs can be installed easily during manufacturing. Furthermore, since the spaces between the inner rings and the outer rings of the roller bearings are used as the deflection ranges of the belleville springs, the axial length of the small gear portion can be shortened without suppressing the maximum deflection amounts of the belleville springs.
  • An eighth invention of the electric power steering device in accordance with the present invention is characterized that, in accordance with the first invention, said circular elastic bodies are belleville springs whose outer circumferential portions are formed so as to be fitted in circular grooves formed on inner circumferential faces of cylindrical concave portions formed at end portions of said small gear.
  • a ninth invention of the electric power steering device in accordance with the present invention is characterized that, in accordance with the first invention, said circular elastic bodies are cylindrical elastic bodies externally fitted over portions of said shaft portions of said small gear between inner rings of said roller bearings and end portions of said gear body of said small gear, and said limiting members are provided at portions of end portions of said small gear inside said cylindrical elastic bodies.
  • the deflection amounts of the cylindrical elastic bodies are limited by the limiting member; hence, the plastic deformation of the cylindrical elastic bodies is prevented, and the durability thereof is improved.
  • cylindrical elastic bodies are wholly cylindrical, unlike the case of the belleville springs, the possibility of causing a mistake of assembling the elastic bodies in the reverse direction is eliminated; hence, the necessity of reassembling the cylindrical elastic bodies is eliminated. Still further, the differences in the dimensions of the inside and outside diameters of the cylindrical elastic bodies are small in comparison with the belleville springs. Therefore, such spring receiving members as those required for the belleville springs are not necessary for the cylindrical elastic bodies; hence, the number of components can be reduced, and the cylindrical elastic bodies can be assembled without increasing the size of the small gear portion.
  • a tenth invention of the electric power steering device in accordance with the present invention is characterized that, in accordance with the ninth invention, said cylindrical elastic bodies are coil springs, and said limiting members are convex members provided so as to be integrated with the end portions of said small gear.
  • FIG. 1 is a schematic enlarged sectional view of a reduction gear mechanism portion, showing the configuration of Embodiment 1 of an electric power steering device in accordance with the present invention
  • FIG. 2 is a schematic sectional view showing the overall configuration of the electric power steering device in accordance with the present invention.
  • the electric power steering device comprises an electric motor 1 for assisting steering, a reduction gear mechanism A, a housing 5 serving as a supporting member for incorporating and supporting the reduction gear mechanism A, and a steering means 6 connected to the reduction gear mechanism A.
  • the reduction gear mechanism A has a worm 3 serving as a small gear connected to the output shaft 1a of the electric motor 1 via a shaft coupling 2 having a male joint portion 21 and a female joint portion 22, and a worm wheel 4 serving as a large gear meshing with this worm 3.
  • the steering means 6 comprises a first steering shaft 61, one end portion of which is connected to a steering wheel B used for steering and the other end portion of which has a cylindrical portion 61a, a torsion bar 62, one end portion of which is inserted into the cylindrical portion 61a of the first steering shaft 61 and connected thereto and which is twisted by the action of steering torque applied on the steering wheel B, and a second steering shaft 63, which is connected to the reduction gear mechanism A and the other end portion of which is connected to the other end portion of the torsion bar 62.
  • the second steering shaft 63 is connected to a rack-and-pinion steering mechanism (not shown), for example, via a universal joint.
  • the housing 5 comprises a first housing portion 5a and a second housing portion 5b.
  • the first housing portion 5a incorporates the worm 3 having shaft portions 3b and 3c, smaller than a gear body 3a in diameter, at both end portions of the gear body 3a having a tooth portion comprising multi-arranged teeth, respectively, and rotatably supports the shaft portions 3b and 3c of the worm 3 via roller bearings 7 and 8, respectively.
  • the second housing portion 5b incorporates the worm wheel 4, and supports the second steering shaft 63, to which the worm wheel 4 is secured, via two roller bearings 9 and 10 fitted on the second steering shaft 63.
  • the first housing portion 5a is configured in a shape extending in the axial direction of the worm 3, and one end portion in the longitudinal direction thereof is provided with a supporting hole 51 in which the roller bearing 7 is internally fitted so as to be supported, a threaded hole 52 connected to this supporting hole 51, and a motor mounting portion 53.
  • a threaded ring 11 for securing the roller bearing 7 is threadably mounted in the threaded hole 52.
  • the electric motor 1 is mounted on the motor mounting portion 53.
  • the other end portion of the first housing portion 5a is provided with a supporting hole 54 in which the roller bearing 8 is internally fitted so as to be supported.
  • the shaft portion 3b of the worm 3 of the reduction gear mechanism A is internally fitted in the inner ring 7a of the roller bearing 7 so as to be movable in the axial direction and is rotatably supported by the housing 5 via the roller bearing 7.
  • the shaft portion 3c provided at the other end portion of the gear body 3a is internally fitted in the inner ring 8a of the roller bearing 8 so as to be movable in the axial direction and is rotatably supported by the housing 5 via the roller bearing 8.
  • the worm wheel 4 is fitted on and secured to the intermediate portion of the second steering shaft 63.
  • belleville springs 12 and 12 serving as circular elastic bodies for suppressing the movement of the worm 3 in the axial direction, circular limiting members 13 and 13 for limiting the deflection amounts of these belleville springs 12 and 12 and spring receiving portions 14 and 14 integrated with these limiting members 13 and 13 and making contact with the outer circumferential portions of the belleville springs 12 and 12 are respectively provided.
  • FIG. 3 is a schematic perspective outline view showing the configuration of the belleville spring 12 serving as a circular elastic body in accordance with Embodiment 1.
  • the inner circumferential portion of the belleville spring 12 is formed as nonflexible flat portions 12a having planes being orthogonal to the center axis line and arranged radially.
  • the outer circumferential portion of the belleville spring 12 is formed as a circular flexible tapered portion 12b inclined with respect to the center axis line.
  • the portion on the side of the center axis away from the end portion of each flat portion 12a is provided with an opening having a size capable of allowing the shaft portions 3b and 3c of the worm 3 to be inserted therethrough.
  • the belleville spring 12 has multiple flexible pieces 12c protruding from the tapered portion 12b to the respective flat portions 12a.
  • the inner circumferential portion of each of the flexible pieces 12c is formed as the flat portion 12a.
  • the belleville springs 12 and 12 are assembled between the inner rings 7a and 8a of the roller bearings 7 and 8 on the shaft portions 3b and 3c of the worm 3 and the limiting members 13 and 13, respectively. More specifically, both the belleville springs 12 and 12 are assembled while the shaft portions 3b and 3c of the worm 3 are inserted through the openings in the central portions thereof, respectively, so that the protruding side faces of the respective flat portions 12a make contact with one side faces of the inner rings 7a and 8a of the roller bearings 7 and 8, and so that the outer circumferential fringes of the tapered portions 12b make contact with the spring receiving portions 14 and 14.
  • the belleville springs 12 and 12 push the inner rings 7a and 8a of the roller bearings 7 and 8 in directions opposite to the gear body 3a of the worm 3, thereby eliminating the clearance between the inner rings 7a and 8a and the clearance between the outer rings 7b and 8b, in other words, the axial clearance between the roller bearings 7 and 8, and suppressing the movement of the worm 3, one way and the other way, in the axial direction with respect to the inner rings 7a and 8a.
  • the limiting members 13 and 13 are circular members externally fitted on the shaft portions 3b and 3c of the worm 3. Both the limiting members 13 and 13 are in contact with the end faces of the gear body 3a, and make contact with the concave side faces of the flat portions 12a in the case where the belleville springs 12 and 12 are deflected, thereby limiting the deflection amounts of the belleville springs 12 and 12.
  • the spring receiving portions 14 and 14 are formed in a disc shape so as to be integrated with the one end portions of the limiting members 13 and 13.
  • the output shaft 1a of the electric motor 1 is coupled to the shaft portion 3b of the worm 3 via the male joint portion 21 and the female joint portion 22 having serrations so as to be relatively movable in the axial direction.
  • the male joint portion 21 is configured by providing a serration on the circumferential face of the shaft portion 3b.
  • the female joint portion 22 is configured by providing a serration on the inside of a cylindrical member fitted in and secured to the output shaft 1a. The male joint portion 21 is fitted in the female joint portion 22 using the serrations.
  • the housing 5 incorporates a torque sensor 15 for detecting the steering torque applied to the steering wheel B and corresponding to the relative rotational displacement amount between the first steering shaft 61 and the second steering shaft 63 depending on the torsion of the torsion bar 62.
  • the device is configured that the electric motor 1 is drive-controlled on the basis of the torque value or the like detected by this torque sensor 15.
  • the shaft portion 3b on the one end portion side of the worm 3 is movably coupled to the output shaft 1a of the electric motor 1 via the shaft coupling 2, and the shaft portion 3b is born by the roller bearing 7 so as to be rotatable and movable in the axial direction.
  • the shaft portion 3c on the other end portion side is born by the roller bearing 8 so as to be rotatable and movable in the axial direction.
  • the belleville springs 12 and 12 and the limiting members 13 and 13 having the spring receiving portions 14 and 14 are assembled between the gear body 3a of the worm 3 and the inner rings 7a and 8a of the roller bearings 7 and 8, respectively.
  • the belleville springs 12 and 12 act to suppress the worm 3 from moving in the axial direction.
  • the steering force of the steering wheel B is transmitted to the worm 3 via the first steering shaft 61, the torsion bar 62, the second steering shaft 63 and the worm wheel 4.
  • the worm 3 is moved, one way or the other way, in the axial direction while deflecting the tapered portion 12b of the one or the other belleville spring 12.
  • FIG. 4 is a schematic sectional view showing a state wherein the limiting member 13 of Embodiment 1 limits the deflection amount of the belleville spring 12 serving as a circular elastic body.
  • the state on the side of the shaft portion 3c of the worm 3 is exemplified in FIG. 4.
  • the deflection amount of the tapered portion 12b of the belleville spring 12 increases, and the shape of the belleville spring 12 becomes flatter than its ordinary shape as a whole.
  • the deflection amount of the tapered portion 12b of the belleville spring 12 can be limited by the limiting member 13.
  • the movement force of the worm 3 is transmitted from the end face of the gear body 3a to the belleville spring 12 via the spring receiving portion 14 provided on the side of the shaft portion 3c, the tapered portion 12b is deflected, and the belleville spring 12 is flattened.
  • the limiting member 13 makes contact with the concave side faces of the flat portions 12a of the belleville spring 12, whereby further movement of the worm 3 to the side of the shaft portion 3c is limited.
  • the deflection amount of the tapered portion 12b of the belleville spring 12 is also limited; therefore, the plastic deformation of the belleville spring 12 is prevented and the durability thereof is improved.
  • the inner circumferential portions of the belleville springs 12 and 12 are formed as flat portions 12a, and each of the limiting members 13 and 13 makes contact with the flat portions 12a to limit the deflection amount of the tapered portion 12b; therefore, the limiting members 13 and 13 can be disposed in the spaces between the inner and outer fringes of the belleville springs 12 and 12, without increasing the size of the portion of the worm 3.
  • each limiting member 13 is disposed in the space between the inner and outer fringes of the belleville spring 12, it is possible to have a configuration wherein multiple limiting members are provided so as to be opposed to the clearances 12d each provided between the adjacent flexible pieces 12c, and in the case where the belleville spring 12 is deflected, each limiting member 13 passes through the clearance 12d and makes contact with one side face of each of the inner rings 7a and 8a.
  • Embodiment 1 described above has a configuration wherein the flat portions 12a formed at the end portions of the flexible pieces 12c of the belleville springs 12 and 12 are used to function as seats opposed to the inner rings 7a and 8a, and the flat portions 12a make face contact with the one side faces of the inner rings 7a and 8a. Therefore, the stability of both the belleville springs 12 and 12 can be raised without using support members for supporting the flexible pieces 12c of both the belleville springs 12 and 12; hence, the number of components can be reduced although the two belleville springs 12 and 12 are provided, and the cost of the electric power steering device can be reduced in comparison with the case wherein the above-mentioned supporting members are used.
  • Embodiment 1 described above has a configuration wherein the limiting members 13 and 13 are provided as components separate from the worm 3, the shaft portions 3b and 3c may be machined so that the limiting members 13 and 13 are formed so as to be integrated with the shaft portions 3b and 3c of the worm 3, in other words, the limiting member 13 is formed integrally.
  • Embodiment 1 is configured that the limiting members 13 and 13 are formed so as to be integrated with the spring receiving portions 14 and 14, the worm 3 may be machined so that the spring receiving portions 14 and 14 are integrated with the gear body 3a of the worm 3, for example.
  • Embodiment 1 is configured that the flat portions 12a of the belleville springs 12 and 12 are made contact with the one side faces of the inner rings 7a and 8a of the roller bearings 7 and 8, respectively, Embodiment 1 may also be configured that the directions of the belleville springs 12 and 12 are reversed, that the flat portions 12a are made contact with the end faces of the gear body 3a of the worm 3, and that the limiting members 13 and 13 and the spring receiving portions 14 and 14 are provided between the belleville springs 12 and 12 and the inner rings 7a and 8a, respectively.
  • the belleville spring 12 is configured to have the flexible pieces 12c on the sides of the flat portions 12a, the belleville spring 12 may also be configured that the flat portions are formed into a circular shape, that the tapered portion 12b is formed into a radial shape, and that the flexible piece 12c is provided for each of the radial portions. Still further, the belleville spring 12 may have a structure wherein the clearances 12d are not provided.
  • FIG. 5 is a schematic enlarged sectional view of a reduction gear mechanism portion, showing the configuration of Embodiment 2 of the electric power steering device in accordance with the present invention.
  • Embodiment 2 of the electric power steering device in accordance with the present invention is configured that, instead of the belleville springs 12 and 12, elastic circular bodies 16 and 16 capable of suppressing the movement of the worm 3 in the axial direction and capable of pushing the worm 3 toward the worm wheel 4 are provided.
  • the worm 3 is rotatably supported on the housing 5 via the roller bearings 7 and 8 and the elastic circular bodies 16 and 16.
  • the elastic circular bodies 16 and 16 are externally fitted on the outer rings 7b and 8b of the roller bearings 7 and 8, respectively, and configured in a nearly L-shape in cross section so as to have first circular portions 16a and 16a for pushing the worm 3 toward the worm wheel 4 and second circular portions 16b and 16b, protruding inward in the radial direction from the one end portions of the first circular portions 16a and 16a and making contact with the side faces of the outer rings 7b and 8b, for suppressing the movement of the worm 3 in the axial direction.
  • the elastic circular bodies 16 and 16 are provided with elastic members 16c and 16c made of rubber and reinforcing members 16d, 16d, 16e and 16e having a nearly L-shape in cross section and laminated inside and outside the elastic members 16c and 16c, respectively.
  • the reinforcing members 16d and 16d provided inside are press-fitted on the outer rings 7b and 8b of the roller bearings 7 and 8, respectively, and the reinforcing members 16e and 16e provided outside are press-fitted in the supporting holes 51 and 54, respectively.
  • the reinforcing members 16d, 16d, 16e and 16e are made of metal or resin and bonded to the elastic members 16c and 16c using a vulcanized adhesive or the like.
  • the pushing of the worm 3 toward the worm wheel 4 by the first circular portions 16a and 16a is made possible, for example, by setting the distance L between the center of the supporting holes 51 and 54 and the center of the supporting holes 75 and 76, in which the roller bearings 9 and 10 are fitted so as to be supported, smaller than the dimension obtained by adding ⁇ d/2, half of the pitch circle diameter ⁇ d of the worm 3, to ⁇ D/2, half of the pitch circle diameter ⁇ D of the worm wheel 4.
  • Embodiment 2 shown in FIG. 5 the elastic restoration forces of the first circular portions 16a and 16a are applied to the worm 3, and the worm 3 is pushed toward the portion meshing with worm wheel 4; hence, the backlash amount at the meshing portion can be reduced.
  • the gear body of the worm wheel 4 is made of synthetic resin to reduce the meshing noise generated when meshing with the worm 3, even in the case where the gear body of the worm wheel 4 is swollen owing to moisture and the swollen gear body is pushed toward the worm 3, the first circular portions 16a and 16a are deflected, and the rotational torque applied to the meshing portion can be reduced.
  • the gear meshing noise owing to the backlash at the meshing portion can be reduced by the elastic circular bodies 16 and 16 for supporting the worm 3, the rotational torque can also be reduced, and the steering feeling in the steering range wherein the electric motor 1 is not driven can be improved.
  • the reduction gear mechanism A in accordance with Embodiments 1 and 2 described above may be a hypoid gear comprising a hypoid pinion serving as a small gear and a hypoid wheel serving as a large gear, instead of the worm gear comprising the worm 3 serving as a small gear and the worm wheel 4 serving as a large gear.
  • the small gear and the large gear may be helical gears or may be gears obtained by combining part of a helical gear and part of a worm gear.
  • the flexible pieces 12c of the belleville spring 12 four in number, equally distributed in the circumferential direction, are exemplified in Embodiment 1, the number of the flexible pieces can be changed variously, provided that they are equally distributed.
  • FIG. 6 is a schematic enlarged sectional view of a reduction gear mechanism portion, showing the configuration of Embodiment 3 of the electric power steering device in accordance with the present invention
  • FIG. 7 is a schematic enlarged sectional view taken on line VII-VII of FIG. 6.
  • the supporting hole 54 provided in the other end portion of the first housing portion 5a of the housing 5, for supporting the roller bearing 8 is configured into an elliptic shape that is made eccentric in a direction wherein the distance H between the rotational centers of the worm 3 and the worm wheel 4 becomes long or short.
  • the roller bearing 8 can be moved in the direction wherein the distance H between the rotational centers of the worm 3 and the worm wheel 4 becomes long or short.
  • a leaf spring 120 being deflected and serving as an energizing means for energizing the roller bearing 8 so that the distance H between the rotational centers of the worm 3 and the worm wheel 4 becomes short, is disposed between the supporting hole 54 and the outer ring 8b of the roller bearing 8 on the opposite side of the worm wheel 4.
  • This leaf spring 120 is deflected in an arch shape along the outer circumferential face of the roller bearing 8 and is formed in a shape being inclined from one fringe to the other fringe in the width direction with respect to the outer circumferential face of the roller bearing 8, whereby deflection is made possible between the supporting hole 54 and the outer ring 8b.
  • the elastic restoration force of the leaf spring 120 energizes the worm 3 via the roller bearing 8 so that the distance H between the rotational centers of the worm 3 and the worm wheel 4 becomes short.
  • the worm 3 of the reduction gear mechanism A has a gear body 3a having multi-arranged teeth and shaft portions 3b and 3c being smaller than the gear body 3a in diameter and connected to both end portions of the gear body 3a via step portions 3d and 3d formed in the radial direction.
  • the one shaft portion 3b is internally fitted in the inner ring 7a of the roller bearing 7 so as to be movable in the axial direction, thereby being rotatably supported by the housing 5 via the roller bearing 7.
  • the other shaft portion 3c is internally fitted in the inner ring 8a of the roller bearing 8 so as to be movable in the axial direction, thereby being rotatably supported by the housing 5 via the roller bearing 8.
  • the worm wheel 4 is fitted on and secured to the intermediate portion of the second steering shaft 63.
  • belleville springs 121 and 121 serving as elastic bodies for suppressing the movement of the worm 3 in the axial direction and convex portions 131 and 131 serving as limiting members for limiting the deflection amounts of the belleville springs 121 and 121 are provided respectively.
  • FIG. 8 is a schematic enlarged perspective view showing the configuration of the belleville spring 121 serving as an elastic body of Embodiment 3.
  • the belleville spring 121 is formed in a taper shape inclined from the inner fringe to the outer fringe with respect to the center axis so as to have flexibility, and from the intermediate portion in the radial direction to the inner fringe, multiple flexible pieces 121a are equally distributed.
  • the portion on the side of the center axis away from the end portion of each flexible piece 121a is provided with an opening having a size capable of allowing the shaft portions 3b and 3c of the worm 3 to be inserted therethrough.
  • the belleville springs 121 and 121 are installed so that the inner fringe portions thereof make contact with the inner rings 7a and 8a, respectively, and so that the outer fringe portions thereof make contact with the step portions 3d and 3d of the shaft portions 3b and 3c of the worm 3, respectively.
  • the belleville springs 121 and 121 push the inner rings 7a and 8a of the roller bearings 7 and 8 in directions opposite to the gear body 3a of the worm 3, thereby eliminating the clearance between the inner rings 7a and 8a and the clearance between the roller bearings 7 and 8, in other words, the axial clearance between the roller bearings 7 and 8, and suppressing the movement of the worm 3, one way and the other way, in the axial direction with respect to the inner rings 7a and 8a.
  • the convex portions 131 and 131 are provided so as to protrude from and be integrated with the worm 3 at multiple places in the circumferential direction at portions on the sides of the step portions 3d and 3d of the shaft portions 3b and 3c and inside the belleville springs 121 and 121.
  • the convex portions 131 and 131 are positioned outside the outer circumferences of the shaft portions 3b and 3c; as the worm 3 moves in the axial direction, the convex portions 131 on the side of the one shaft portion 3b make contact with the side face of the inner ring 7a of the roller bearing 7 on the side of the gear body 3a, or the convex portions 131 on the side of the other shaft portion 3c make contact with the side face of the inner ring 8a of the roller bearing 8 on the side of the gear body 3a, thereby limiting the deflection amounts of the belleville springs 121 and 121, respectively.
  • the shaft portion 3b on the one end portion side of the worm 3 is movably coupled to the output shaft 1a of the electric motor 1 via the shaft coupling 2, and the shaft portion 3b is born by the roller bearing 7 so as to be rotatable and movable in the axial direction.
  • the shaft portion 3c on the other end portion side is born by the roller bearing 8 so as to be rotatable and movable in the axial direction.
  • the belleville springs 121 and 121 are provided between the inner rings 7a and 8a of the roller bearings 7 and 8 and the step portions 3d and 3d of the worm 3, respectively.
  • the belleville springs 121 and 121 act to suppress the movement of the worm 3 in the axial direction.
  • the steering force of the steering wheel B is transmitted to the worm 3 via the first steering shaft 61, the torsion bar 62, the second steering shaft 63 and the worm wheel 4.
  • the worm 3 is moved one way in the axial direction while deflecting the flexible pieces 121a of the one belleville spring 121 or the other way in the axial direction while deflecting the flexible pieces 121a of the other belleville spring 121.
  • the deflection amounts of the flexible pieces 121a of the one belleville spring 121 increase; however, the deflection amounts of the flexible pieces 121a of the belleville spring 121 can be limited by the convex portions 131.
  • the movement force of the worm 3 is transmitted from the step portion 3d to the belleville spring 121; hence, the flexible pieces 121a of the belleville spring 121 are deflected, and the belleville spring 121 is flattened wholly.
  • the deflection amounts of the flexible pieces 121a increase, the convex portions 131 make contact with the one side face (the face opposed to the side of the gear body 3a of the worm 3) of the inner ring 7a or 8a; hence, the movement of the worm 3 can be limited.
  • the deflection amounts of the belleville springs 121 and 121 are also limited; therefore, the plastic deformation of the belleville springs 121 and 121 is prevented and the durability thereof is improved.
  • step portions 3d and 3d provided at both end portions of the gear body 3a of the worm 3 function as seats for receiving the belleville springs 121 and 121; hence, the structure for supporting the belleville springs 121 and 121 is simplified, and the machinability and assembly workability are improved.
  • the limiting members can be provided without increasing the number of components; hence, the assembly workability is improved, and the cost is reduced although the limiting members are provided.
  • the roller bearing 8 incorporated in the first housing portion 5a of the housing 5 and used to bear the shaft portion 3c of the worm 3 is energized in a direction wherein the distance H between the rotational centers of the worm 3 and the worm wheel 4 becomes short.
  • the backlash amount at the meshing portion of the worm 3 and the worm wheel 4 can be reduced; besides, even in the case where the abrasion amounts of the teeth of the worm 3 and the worm wheel 4 increase, the backlash amount at the meshing portion can be reduced.
  • Embodiment 3 described above has a configuration wherein the convex portions 131 and 131 serving as limiting members are provided so as to be integrated with the shaft portions 3b and 3c, limiting members formed into a circular shape, for example, separate from the shaft portions 3b and 3c, may be externally fitted on the shaft portions 3b and 3c. Furthermore, the limiting members may be structured so as to be continuous around the outer circumferences of the shaft portions 3b and 3c of the worm 3, or may have one convex portion or multiple convex portions spaced in the circumferential direction.
  • the limiting members can also be configured, for example, that the portions between the adjacent flexible pieces 121a of the belleville spring 121 are deflected to the protruding side of the belleville spring 121 in parallel with the center axis line and that the bent portions are used as limiting members.
  • the belleville spring 121 of Embodiment 3 described above has a structure wherein the flexible pieces 121a are provided in the inner circumferential portion
  • the belleville spring 121 may have a structure wherein the flexible pieces 121a are provided in the outer circumferential portion.
  • the belleville spring 121 may have a structure wherein the flexible pieces 121a are not provided.
  • the leaf spring 120 is used as an energizing means for energizing the roller bearing 8 in the direction wherein the distance H between the rotational centers of the worm 3 and the worm wheel 4 becomes short
  • an elastic body such as synthetic resin having flexibility, rubber or coil spring, may also be used as the energizing means.
  • the reduction gear mechanism A in accordance with Embodiment 3 described above may be a hypoid gear comprising a hypoid pinion serving as a small gear and a hypoid wheel serving as a large gear, instead of the worm gear comprising the worm 3 serving as a small gear and the worm wheel 4 serving as a large gear.
  • the small gear and the large gear may be helical gears or may be gears obtained by combining part of a helical gear and part of a worm gear.
  • Embodiments 4 and 5 of the electric power steering device in accordance with the present invention will be described below.
  • FIG. 9 is a schematic enlarged sectional view of a reduction gear mechanism portion, showing the configuration of Embodiment 4 of the electric power steering device in accordance with the present invention.
  • the worm 3 of the reduction gear mechanism A has a gear body 3a having a tooth portion with multi-arranged teeth and shaft portions 3b and 3c being smaller than the gear body 3a in diameter and connected to both end portions of the gear body 3a via step portions 3d and 3d formed in the radial direction.
  • the one shaft portion 3b is internally fitted in the inner ring 7a of the roller bearing 7 so as to be movable in the axial direction, thereby being rotatably supported by the housing 5 via the roller bearing 7.
  • the other shaft portion 3c is internally fitted in the inner ring 8a of the roller bearing 8 so as to be movable in the axial direction, thereby being rotatably supported by the housing 5 via the roller bearing 8.
  • the worm wheel 4 is fitted on and secured to the intermediate portion of the second steering shaft 63.
  • circular grooves 71 and 81 are each formed on the inner circumferential face between the raceway groove and the side face of the gear body 3a of the worm 3.
  • belleville springs 122 and 122 serving as elastic bodies for suppressing the movement of the worm 3 in the axial direction and convex portions 132 and 132 serving as limiting members for limiting the deflection amounts of the belleville springs 122 and 122 are provided, respectively.
  • sealing members 72 and 82 for respectively sealing the space between the inner ring 7a and the outer ring 7b and the space between the inner ring 8a and the outer ring 8b are fitted and secured.
  • FIG. 10 is a schematic enlarged perspective view showing the configuration of the belleville spring 122 serving as an elastic body of Embodiment 4.
  • the belleville spring 122 is formed into a flexible taper shape inclined with respect to the center axis line from the fitting inner circumferential portions 122a, being flat and orthogonal to the center axis line, to the outer fringe.
  • the portion on the side of the center axis away from the end portion of each flat fitting inner circumferential portion 122a is provided with an opening having a size capable of allowing the shaft portions 3b and 3c of the worm 3 to be inserted therethrough.
  • the belleville spring 122 has multiple flexible pieces 122b protruding from the intermediate portion in the radial direction to the inner fringe, and the fitting inner circumferential portion 122a is provided at the end portion of each flexible piece 122b.
  • the belleville springs 122 and 122 are installed so that the fitting inner circumferential portions 122a thereof are externally fitted in the circular grooves 71 and 81 of the inner rings 7a and 8a, respectively, and so that the outer circumferential portions thereof make contact with the step portions 3d and 3d, respectively.
  • the belleville springs 122 and 122 push the inner rings 7a and 8a of the roller bearings 7 and 8 in directions opposite to the gear body 3a of the worm 3, thereby eliminating the clearance between the inner rings 7a and 8a and the clearance between the outer rings 7b and 8b, in other words, the axial clearance between the roller bearings 7 and 8, and suppressing the movement of the worm 3, one way and the other way, in the axial direction with respect to the inner rings 7a and 8a.
  • the convex portions 132 and 132 protrude on the sides of the step portions 3d and 3d of both the shaft portions 3b and 3c of the worm 3 at portions inside the outer circumferential portions of the belleville springs 122 and 122, in other words, protrude on the sides of the step portions 3d and 3d inside the outer circumferential portions of the belleville springs 122 and 122 around the entire outer circumferences of the shaft portions 3b and 3c between the inner rings 7a and 8a and the step portions 3d and 3d, respectively, so as to be integrated with the shaft portions 3b and 3c, respectively.
  • the convex portions 132 and 132 are formed so as to be larger in diameter than the shaft portions 3b and 3c.
  • the convex portion 132 on the side of the one shaft portion 3b makes contact with the side face of the inner ring 7a of the roller bearing 7 on the side of the gear body 3a, or the convex portion 132 on the side of the other shaft portion 3c makes contact with the side face of the inner ring 8a of the roller bearing 8 on the side of the gear body 3a, thereby limiting the deflection amounts of the belleville springs 122 and 122.
  • the shaft portion 3b on the one end portion side of the worm 3 is movably coupled to the output shaft 1a of the electric motor 1 via the shaft coupling 2, and the shaft portion 3b is born by the roller bearing 7 so as to be rotatable and movable in the axial direction, and the shaft portion 3c on the other end portion side is born by the roller bearing 8 so as to be rotatable and movable in the axial direction.
  • the belleville springs 122 and 122 are provided between the inner rings 7a and 8a of the roller bearings 7 and 8 and the step portions 3d and 3d of the worm 3, respectively. Furthermore, the belleville springs 122 and 122 act to suppress the movement of the worm 3 in the axial direction.
  • the steering force of the steering wheel B is transmitted to the worm 3 via the first steering shaft 61, the torsion bar 62, the second steering shaft 63 and the worm wheel 4.
  • the worm 3 is moved, one way or the other way, in the axial direction while deflecting the flexible pieces 122b of the one or the other belleville spring 122.
  • the deflection amounts of the flexible pieces 122b of the one belleville spring 122 increase; however, the deflection amounts of the flexible pieces 122b of this belleville spring 122 can be limited by the convex portion 132.
  • the movement force of the worm 3 is transmitted from the step portion 3d to the belleville spring 122; hence, the flexible pieces 122b of the belleville spring 122 are deflected, and the belleville spring 122 is flattened wholly.
  • both the belleville springs 122 and 122 are externally fitted in the circular grooves 71 and 81 respectively formed in the inner rings 7a and 8a of both the roller bearings 7 and 8, the belleville springs 122 and 122 can be assembled beforehand in the roller bearings 7 and 8, respectively; hence, it is not necessary to assemble both the belleville springs 122 and 122 individually. Therefore, such a mistake of reversing the directions of both the belleville springs 122 and 122 during assembly is not caused; hence, it is possible to eliminate the necessity of reassembling the belleville springs 122 and 122, and the assembly workability can be improved. Furthermore, when the worm 3 moves in the axial direction, the convex portions 132 and 132 can be made contact with the one side faces of the inner rings 7a and 8a, respectively, without interfering with both the belleville springs 122 and 122.
  • the limiting members can be provided without increasing the number of components; hence, the assembly workability is improved, and the cost is reduced although the limiting members are provided.
  • FIG. 11 is a schematic enlarged sectional view of a reduction gear mechanism portion, showing the configuration of Embodiment 5 of the electric power steering device in accordance with the present invention
  • FIG. 12 is a schematic enlarged view of a portion on the side of one shaft portion 3c of the worm 3 of Embodiment 5.
  • Embodiment 5 of the electric power steering device in accordance with the present invention is configured that the outer circumferential portions of the belleville springs 122 and 122 are assembled in both the step portions 3d and 3d of the worm 3, respectively, and that the inner circumferential portions thereof are made contact with the one side faces (the faces opposed to the sides of the gear body 3a of the worm 3) of the inner rings 7a and 8a.
  • circular concave portions 31 and 31 being dent in the axial direction are formed in the step portions 3d and 3d of both the shaft portions 3b and 3c, respectively.
  • the end faces of both the shaft portions 3b and 3c are formed into a cylindrical shape.
  • circular grooves 32 and 32 being dent outward are formed in the inner circumferential portions of the outer circumferential wall faces of the circular concave portions 31 and 31, respectively.
  • the belleville spring 122 is formed into a flexible taper shape inclined with respect to the center axis line from the fitting outer circumferential portion 122c, being flat and orthogonal to the center axis line, to the inner fringe.
  • the portion on the side of the center axis away from the end portion of each fitting outer circumferential portion 122c is provided with an opening having a size capable of allowing the shaft portions 3b and 3c of the worm 3 to be inserted therethrough.
  • the belleville spring 122 has multiple flexible pieces 122b protruding from the intermediate portion in the radial direction to the inner fringe.
  • the belleville springs 122 and 122 are installed so that the fitting outer circumferential portions 122c are internally fitted in the circular grooves 32 and 32 formed in the step portions 3d and 3d of both end portions of the worm 3 and so that the inner circumferential portions make contact with the one side faces of the inner rings 7a and 8a.
  • the belleville springs 122 and 122 push the inner rings 7a and 8a of the roller bearings 7 and 8, respectively, in directions toward the gear body 3a of the worm 3.
  • Embodiments 4 and 5 described above have a configuration wherein the convex portions 132 and 132 serving as limiting members are formed so as to be integrated with the shaft portions 3b and 3c; however, in addition to this configuration, limiting members formed in a circular shape, for example, and serving as components separate from the shaft portions 3b and 3c, may be externally fitted on the shaft portions 3b and 3c. Furthermore, although the limiting members are formed so as to be continuous around the outer circumferences of both the shaft portions 3b and 3c, the limiting members may have one convex portion or multiple convex portions spaced in the circumferential directions of the shaft portions 3b and 3c.
  • the limiting members can also be configured, for example, that the portions between the adjacent flexible pieces 122b of the belleville spring 122 are deflected to the protruding side of the belleville spring 122 in parallel with the center axis line and that the bent portions are used as limiting members.
  • the belleville springs 122 and 122 of Embodiments 4 and 5 described above have a structure wherein the flexible pieces 122b are provided in the inner circumferential portion; however, in addition to this structure, the belleville springs 122 and 122 may have a structure wherein the flexible pieces 122b are provided in the outer circumferential portion. Furthermore, the belleville springs 122 and 122 may have a structure wherein the flexible pieces 122b are not provided.
  • the reduction gear mechanism A in accordance with Embodiments 4 and 5 described above may be a hypoid gear comprising a hypoid pinion serving as a small gear and a hypoid wheel serving as a large gear, instead of the worm gear comprising the worm 3 serving as a small gear and the worm wheel 4 serving as a large gear.
  • the small gear and the large gear may be helical gears or may be gears obtained by combining part of a helical gear and part of a worm gear.
  • Embodiments 6, 7 and 8 of the electric power steering device in accordance with the present invention will be described below.
  • FIG. 13 is a schematic enlarged sectional view of a reduction gear mechanism portion, showing the configuration of Embodiment 6 of the electric power steering device in accordance with the present invention.
  • the worm 3 of the reduction gear mechanism A has a gear body 3a having a tooth portion with multi-arranged teeth and shaft portions 3b and 3c being smaller than the gear body 3a in diameter and connected to both end portions of the gear body 3a via step portions 3d and 3d formed in the radial direction.
  • the one shaft portion 3b is internally fitted in the inner ring 7a of the roller bearing 7 so as to be movable in the axial direction, thereby being rotatably supported by the housing 5 via the roller bearing 7.
  • the other shaft portion 3c is internally fitted in the inner ring 8a of the roller bearing 8 so as to be movable in the axial direction, thereby being rotatably supported by the housing 5 via the roller bearing 8.
  • the worm wheel 4 is fitted on and secured to the intermediate portion of the second steering shaft 63.
  • Coil springs 123 and 123 serving as cylindrical elastic bodies for suppressing the movement of the worm 3 in the axial direction and convex portions 133 and 133 serving as limiting members for limiting the deflection amounts of the coil springs 123 and 123 are provided between the inner ring 7a of the bearing 7 and the step portion 3d on the side of the shaft portion 3b of the worm 3 and between the inner ring 8a of the bearing 8 and the step portion 3d on the side of the shaft portion 3c, respectively, the shaft portion 3b and the shaft portion 3c of the worm 3 being born by the roller bearings 7 and 8 so as to be movable in the axial direction.
  • the coil springs 123 and 123 are externally fitted over the shaft portions 3b and 3c between the inner rings 7a and 8a and the step portions 3d and 3d, the seats on one end portions thereof make contact with the one side faces of the inner rings 7a and 8a, respectively, and the seats on the other end portions thereof make contact with the step portions 3d and 3d, respectively.
  • both the coil springs 123 and 123 can deflect by the distances between the inner rings 7a and 8a and the convex portions 3d and 3d; hence, the movement of the worm 3, one way and the other way, in the axial direction with respect to the inner rings 7a and 8a is suppressed.
  • the convex portions 133 and 133 protrude on the sides of the step portions 3d and 3d of both the shaft portions 3b and 3c of the worm 3 at portions inside the outer circumferential portions of the coil springs 123 and 123, in other words, protrude on the sides of the step portions 3d and 3d inside the outer circumferential portions of the coil springs 123 and 123 around the entire outer circumferences of the shaft portions 3b and 3c between the inner rings 7a and 8a and both the step portions 3d and 3d, respectively, so as to be integrated with the shaft portions 3b and 3c, respectively.
  • the convex portions 133 and 133 are formed so as to be larger in diameter than the shaft portions 3b and 3c, but the diameters thereof are made smaller than the inside diameters of the coil springs 123 and 123.
  • the convex portion 133 on the side of the one shaft portion 3b makes contact with the side face of the inner ring 7a of the roller bearing 7 on the side of the gear body 3a, or the convex portion 133 on the side of the other shaft portion 3c makes contact with the side face of the inner ring 8a of the roller bearing 8 on the side of the gear body 3a, thereby limiting the deflection amounts of the coil springs 123 and 123.
  • the shaft portion 3b on the one end portion side of the worm 3 is movably coupled to the output shaft 1a of the electric motor 1 via the shaft coupling 2, and the shaft portion 3b is born by the roller bearing 7 so as to be rotatable and movable in the axial direction, and the shaft portion 3c on the other end portion side is born by the roller bearing 8 so as to be rotatable and movable in the axial direction.
  • the coil springs 123 and 123 are provided between the step portions 3d and 3d on both sides of the gear body 3a of the worm 3 and the inner rings 7a and 8a of the roller bearings 7 and 8, respectively. Furthermore, both the coil springs 123 and 123 act to suppress the movement of the worm 3 in the axial direction.
  • the steering force of the steering wheel B is transmitted to the worm 3 via the first steering shaft 61, the torsion bar 62, the second steering shaft 63 and the worm wheel 4.
  • the worm 3 is moved, one way or the other way, in the axial direction while deflecting the one or the other coil spring 123.
  • the deflection amount of the one coil spring 123 increases; however, the deflection amount of the coil spring 123 can be limited by the convex portions 133.
  • the movement force of the worm 3 is transmitted from the one step portion 3d to the one coil spring 123; hence, the coil spring 123 is deflected.
  • the convex portion 133 makes contact with the one side face (the face opposed to the side of the gear body 3a of the worm 3) of the inner ring 7a or 8a; hence, the movement of the worm 3 can be limited.
  • the deflection amount of the coil spring 123 is also limited; therefore, the plastic deformation of the coil spring 123 is prevented and the durability thereof is improved.
  • the limiting members can be provided without increasing the number of components; hence, the assembly workability is improved, and the cost is reduced although the limiting members are provided.
  • FIG. 14 is a schematic enlarged sectional view of a reduction gear mechanism portion, showing the configuration of Embodiment 7 of the electric power steering device in accordance with the present invention.
  • Embodiment 7 of the electric power steering device in accordance with the present invention being configured that the shaft portion 3b of the worm 3 is movably coupled to the output shaft 1a, a through hole 23 passing through in the radial direction is formed in part of the female joint portion 22 into which the male joint portion 21 is inserted, and a pushing member 41 having flexibility is inserted into the through hole 23 so as to be held therein.
  • the pushing member 41 pushes the male joint portion 21 in the radial direction, thereby reducing the wobble of the male joint portion 21 with respect to the female joint portion 22 in the radial and circumferential directions.
  • the pushing member 41 is formed of a short shaft member having flanges 41a and 41b on both end portions thereof and wholly made of a material having flexibility, such as rubber or synthetic resin.
  • the one flange 41a inserted from the through hole 23 into the female joint portion 22 pushes the male joint portion 21 in the radial direction
  • the gap between the male joint portion 21 and the female joint portion 22 is flanked on one side in the radial direction; furthermore, since the outer circumferential face of the female joint portion 22 is held between both the flanges 41a and 41b, the pushing member 41 is prevented from dropping from the through hole 23.
  • the male joint portion 21 is inserted into the female joint portion 22 while the pushing member 41 is inserted and held in the through hole 23 of the female joint portion 22, for example.
  • FIG. 15 is a schematic enlarged sectional view of a reduction gear mechanism portion, showing the configuration of Embodiment 8 of the electric power steering device in accordance with the present invention.
  • Embodiment 8 of the electric power steering device in accordance with the present invention instead of the pushing member 41 formed of a short shaft member having the flanges 41a and 41b on both end portions thereof in accordance with Embodiment 7 described above, a pushing member 42 having flexibility and formed of a short shaft member having a flange 42a only on one end portion thereof is inserted into a through hole 23 formed in the radial direction in part of the female joint portion 22 so as to be held therein. With this configuration, the pushing member 42 pushes the male joint portion 21 in the radial direction, thereby reducing the wobble of the male joint portion 21 with respect to the female joint portion 22 in the radial and circumferential directions.
  • the through hole 23 has a circular groove 23a at an intermediate position in the direction of the depth thereof on a plane in parallel with the axial direction, and the flange 42a is inserted into this circular groove 23a; hence, the pushing member 42 is prevented from dropping from the through hole 23.
  • Embodiments 6, 7 and 8 described above have a configuration wherein the convex portions 133 and 133 serving as limiting members are provided so as to be integrated with the shaft portions 3b and 3c; however, in addition to this configuration, limiting members formed into a circular shape, for example, separate from the shaft portions 3b and 3c, may be externally fitted on the shaft portions 3b and 3c. Furthermore, the limiting members may be structured so as to be continuous around the entire outer circumferences of the shaft portions 3b and 3c; still further, the limiting members may have one convex portion or multiple convex portions spaced and arranged in the circumferential directions of the shaft portions 3b and 3c.
  • the coil spring 123 is used as a cylindrical elastic body in Embodiments 6, 7 and 8 described above, the cylindrical elastic body may be a rubber pipe, a bellows or the like having flexibility, and its configuration is not limited particularly.
  • the reduction gear mechanism A in accordance with Embodiments 6, 7 and 8 described above may be a hypoid gear comprising a hypoid pinion serving as a small gear and a hypoid wheel serving as a large gear, instead of the worm gear comprising the worm 3 serving as a small gear and the worm wheel 4 serving as a large gear.
  • the small gear and the large gear may be helical gears or may be gears obtained by combining part of a helical gear and part of a worm gear.
  • the limiting members for limiting the deflection amounts of the circular elastic bodies can be provided at portions along the outer circumferences of the above-mentioned shaft portions respectively at both end portions of the gear body without increasing the size of the small gear portion; hence, it is not necessary to increase the size of the worm serving as the small gear.
  • the deflection amounts of the circular elastic bodies can be limited by the limiting members; hence, the plastic deformation of the circular elastic bodies can be prevented and the durability thereof can be improved.
  • the stability of the belleville springs can be raised without using support members for supporting the flexible pieces of the belleville springs.
  • the number of components can be reduced although the belleville springs are provided, and the cost can be reduced in comparison with the case wherein the supporting members are used.
  • positioning means for determining the circumferential positions of the belleville springs are not necessary, the number of man-hours required for working and the number of man-hours required for assembly can be reduced in comparison with the case wherein such positioning means are provided, and the cost is further reduced.
  • steering feeling in the case where steering is performed left or right from the steering neutral position can be improved, and the durability of the elastic bodies for suppressing the movement of the small gear can be improved; furthermore, even in the case where the abrasion amounts of the teeth increase, the backlash amount at the meshing portion is reduced.
  • the structure for supporting the elastic bodies is simplified; hence, the machinability and assembly workability are improved.
  • the belleville springs are assembled easily, and the lengths of the shaft portions of the small gear in the axial direction can be shortened without suppressing the maximum deflection amounts of the belleville springs.
  • steering feeling in the case where steering is performed left or right from the steering neutral position can be improved, and the durability of the elastic bodies for suppressing the movement of the small gear can be improved; furthermore, the possibility of causing improper direction during the assembly of the elastic bodies is eliminated; hence, it is possible to eliminate the necessity of reassembling the elastic bodies.
  • steering feeling in the case where steering is performed left or right from the steering neutral position can be improved, and the durability of the cylindrical elastic bodies can be improved; furthermore, the possibility of causing improper direction that may occur in the case of the assembly of the belleville springs is eliminated; hence, it is possible to eliminate the necessity of reassembling the cylindrical elastic bodies; moreover, the number of components can be reduced, and the cylindrical elastic bodies can be provided without increasing the size of the small gear portion.
  • steering feeling can be improved further, and the limiting members can be provided without increasing the number of components; hence, the assembly workability is improved, and the cost is reduced although the limiting members are provided.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Power Steering Mechanism (AREA)
  • Gear Transmission (AREA)
EP04728046A 2003-04-18 2004-04-16 Elektrische servolenkvorrichtung Expired - Fee Related EP1623908B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP11170816A EP2371675B1 (de) 2003-04-18 2004-04-16 Elektrische Servolenkung

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
JP2003114018 2003-04-18
JP2003114020 2003-04-18
JP2003118168 2003-04-23
JP2003118167 2003-04-23
PCT/JP2004/005522 WO2004091997A1 (ja) 2003-04-18 2004-04-16 電動パワーステアリング装置

Related Child Applications (2)

Application Number Title Priority Date Filing Date
EP11170816A Division EP2371675B1 (de) 2003-04-18 2004-04-16 Elektrische Servolenkung
EP11170816.0 Division-Into 2011-06-21

Publications (3)

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EP1623908A1 true EP1623908A1 (de) 2006-02-08
EP1623908A4 EP1623908A4 (de) 2007-09-05
EP1623908B1 EP1623908B1 (de) 2012-03-07

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EP11170816A Expired - Fee Related EP2371675B1 (de) 2003-04-18 2004-04-16 Elektrische Servolenkung

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Country Status (4)

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US (1) US7575090B2 (de)
EP (2) EP1623908B1 (de)
JP (1) JP4107326B2 (de)
WO (1) WO2004091997A1 (de)

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EP2450262A1 (de) * 2010-11-09 2012-05-09 JTEKT Corporation Elektrisches Servolenksystem
EP2508768A1 (de) * 2011-03-21 2012-10-10 Maxon Motor AG Federscheibe sowie Lagervorrichtung mit einer Federscheibe
WO2019206367A1 (de) * 2018-04-23 2019-10-31 Kiekert Ag Stelleinheit für kraftfahrzeugtechnische anwendungen insbesondere kraftfahrzeugtürverschlüsse

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KR102635281B1 (ko) * 2017-02-01 2024-02-13 에이치엘만도 주식회사 전동식 동력 보조 조향장치의 감속기
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Cited By (9)

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Publication number Priority date Publication date Assignee Title
EP1783033A2 (de) 2005-11-02 2007-05-09 Mando Corporation Elektroservolenkung mit einem Spielausgleich beim Schneckengetriebe
EP1783033A3 (de) * 2005-11-02 2011-09-07 Mando Corporation Elektroservolenkung mit einem Spielausgleich beim Schneckengetriebe
EP2450262A1 (de) * 2010-11-09 2012-05-09 JTEKT Corporation Elektrisches Servolenksystem
US8459402B2 (en) 2010-11-09 2013-06-11 Jtekt Corporation Electric power steering system
EP2508768A1 (de) * 2011-03-21 2012-10-10 Maxon Motor AG Federscheibe sowie Lagervorrichtung mit einer Federscheibe
CN102734321A (zh) * 2011-03-21 2012-10-17 麦克森发电机股份公司 弹簧垫圈以及包括弹簧垫圈的轴承座
US8845202B2 (en) 2011-03-21 2014-09-30 Maxon Motor Ag Spring washer and a bearing block including a spring washer
CN102734321B (zh) * 2011-03-21 2015-01-07 麦克森发电机股份公司 弹簧垫圈以及包括弹簧垫圈的轴承座
WO2019206367A1 (de) * 2018-04-23 2019-10-31 Kiekert Ag Stelleinheit für kraftfahrzeugtechnische anwendungen insbesondere kraftfahrzeugtürverschlüsse

Also Published As

Publication number Publication date
EP2371675B1 (de) 2012-10-17
WO2004091997A1 (ja) 2004-10-28
US20070102228A1 (en) 2007-05-10
JP4107326B2 (ja) 2008-06-25
EP1623908A4 (de) 2007-09-05
US7575090B2 (en) 2009-08-18
EP2371675A1 (de) 2011-10-05
EP1623908B1 (de) 2012-03-07
JPWO2004091997A1 (ja) 2006-07-06

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